Because of the high cost of producing aluminum, recycling aluminum products has become a cost effective utilization of aluminum resources. However, recycling has its own challenges, especially with respect to used beverage cans (UBC's). A requirement in recycling UBC's is the removal of exterior surface coating, paint and/or ink, as well as removal of interior surface protective coating that prevents the beverage from contacting the aluminum. The removal of coatings is referred to in the industry as delacquering. The amount of coating on a can varies from about 3 wt % to about 4.5 wt %.
Presently, delacquering is accomplished by heating the UBC's to high temperatures, usually in excess of 500 C. and combusting the organic component of the coating(s). An undesirable concurrent process during delaquering is the conversion of some of the base metal to oxides and hydroxides. Such conversions reduce the yield of metal recovered in the recycling process. In addition, the use of a high temperature furnace is a large component of energy and cost in the recycling process.
Hence, there is a need for a method of removing the exterior paint/ink and the interior protective coating from UBCs that removes the organic component of the coatings but does not appreciably affect the base metal.